title: Reference values for CSF outflow resistance and intracranial pressure in healthy elderly.
abstract: OBJECTIVE
  The intracranial pressure (ICP) and CSF outflow resistance (R(out)) are essential to describe the dynamics of the CSF system. R(out) affects ICP, pulse amplitudes, CSF absorption, and the compliance of the system. The objective of this study was to determine the reference values in healthy elderly subjects.
  
  
  METHODS
  Elderly people (60-82 years), who considered themselves healthy, were recruited through an advertisement in the local newspaper. All were evaluated with a 3-T MRI. Subjects were eligible if they did not have any psychiatric or neurologic disorder or signs of advanced atherosclerotic disease. CSF resting pressure (ICP) and R(out) were determined by a constant pressure infusion method with the patient in the supine position. The study population consisted of 40 subjects (mean age 70 years; 23 women).
  
  
  RESULTS
  The median ICP was 11.6 mm Hg (15.8 cmH(2)O) and the reference interval was ICP 7.8-14.3 mm Hg (10.6-19.4 cmH(2)O) (defined as 5th to 95th percentiles). The median R(out) was 8.6 mm Hg/mL/min. The variation in R(out) was large and not normally distributed. The 90th percentile of R(out) was 17.4 mm Hg/mL/min.
  
  
  CONCLUSIONS
  This study reports reference values for ICP and R(out) and should be used for comparison when investigating disorders with suspected CSF dynamic disturbances in the elderly. ICP was in the same range as that reported in the young and middle-aged. The upper limit of R(out) was higher than previously believed to be the upper limit of normal for this age group.
authors.affiliation: Department of Clinical Neuroscience, Umeå University, SE-901 85 Umeå, Sweden. Jan.Malm@neuro.umu.se
authors.forename: Jan
authors.initials: J
authors.lastname: Malm
authors.forename: Johan
authors.initials: J
authors.lastname: Jacobsson
authors.forename: Richard
authors.initials: R
authors.lastname: Birgander
authors.forename: Anders
authors.initials: A
authors.lastname: Eklund
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002555:Cerebrospinal Fluid / Q000502:physiology*; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology*; D015577:Geriatric Assessment; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D012016:Reference Values; D013129:Spinal Puncture